Design time support error using RadButton in Sitefinity
When I add a RadButton to either a usercontrol or Master Page and click on the design time support button (that button with the arrow that appears in design view) it displays an error message.
Error Creating Panel
Property accessor 'Skin' on object 'Telerik.Web.Design.RadButton' on DesignerActionList threw the following exception:
'Unable to cast object of type 'Telerik.Web.UI.RadButton' to type 'Telerik.Web.ISkinnableControl'
RadButton inherits directly from RadWebControl, which implements the ISkinnableControl interface. Make sure you have installed the RadControls properly and you don't have a problem with your Visual Studio, since the RadButton works properly and can be skinned with its embedded skins and with external ones. For more information you can take a look at this video demonstrating how the default behavior looks on our side.
the Telerik team